The faucet assemblies most commonly used today for controlling the flow of hot and cold water to a water basin, tub, or shower, or other washing facility are of three basic types, namely, (A) hot and cold water faucets each having a valve controlled by a handle, usually spaced on opposite sides of the water outlet and being respectively connected to hot and cold water lines, wherein the hot and cold water are mixed downstream of the valves prior to exiting from the outlet into the washing facility; (B) faucets having a single valve controlled by a single handle, usually mounted centrally of the water outlet, and being connected in tandem to hot and cold water lines, wherein the single valve regulates and mixes the flow as an integral function; and (C) faucets like type B except having two handles, normally differentiated in shape and movement, one for controlling volume and the other for controlling temperature.
In each type of faucet briefly described above, movement of the handle(s) to control water flow is a rotational movement. In type A, the dual handles pivot on spaced vertical axes; in type B, the single handle may be push-pull and rotational on a 45.degree. axis or may rotate on a ball or universal joint; and in type C, the handles usually rotate about a common horizontal axis.
Dual handle faucets of type A are inexpensive, accurate, and are widely used. They are generally comprehensible but can be confusing to operate even if the handles are installed in the conventional way to rotate in opposite directions, namely, one clockwise and the other counterclockwise. Such confusion is compounded if the handles are intentionally or inadvertently installed to rotate in the same direction. Moreover, rotational directions in shower installations are sometimes the same and sometimes different so that confusion can result, especially if the handles are adjusted when the bather is facing away from the controls or has soap in the eyes. The conventional dual handle faucets described above require two hands to regulate water volume and temperature simultaneously. In addition, such dual handle faucets do not provide a good visual or tactile indication of water temperature.
Type B single handle faucets can of course be operated with one hand but lack good temperature indication. They employ complex and expensive mixing valves and are embodied in so many modes of operation as to be confusing to the unaccustomed user. More importantly, there is no sure way to regulate volume without affecting temperature, resulting in repeated readjustment, trial and error temperature control, and a corresponding waste of water and energy. Two handle mixing faucets of type C do allow limited single-handed operation and may have an inscribed temperature scale, but they are as complex and expensive as single handle faucets and are more difficult to operate.
In addition to the foregoing, other types of dual-handle faucets that can be operated with one hand have been disclosed, although they are not known to be in common use. An example is in the U.S. Patent to Kempler U.S. Pat. No. 3,903,926. Such faucets lack good temperature indication and have other drawbacks, such as complex internal mixing valves; unitized construction wherein handles, valves and spouts are integrated in a single housing; integral spouts; and surface mounted valve housings. These faucets reveal a clear intent to apply solely to lavatories and solely to surface-mounted conditions requiring finished faucet castings. Moreover, these known faucets utilize pivoting handles requiring close coupling of valve stems with the pivoting mechanism in order to restrict the required arcuate travel of the handles, thereby preventing concealment of valves below surfaces of varying dimensions.
Pivoting handles have the additional drawback of being difficult or impossible to operate by persons with physical disabilities if the shape of the handle requires specific finger manipulation or a twisting motion. Handles moving linearly can be easily operated regardless of the shape of the handles.
A faucet with dual handles that do not pivot but move on linear paths is disclosed in the German Patent to Killias, No. 19 56 161, but this faucet has a complex mixing valve and, in addition, has all the disadvantages of the type C faucets noted above.